Interplay between the NADP-Linked Thioredoxin and Glutathione Systems in Arabidopsis Auxin Signaling

Intracellular redox status is a critical parameter determining plant development in response to biotic and abiotic stress. Thioredoxin (TRX) and glutathione are key regulators of redox homeostasis, and the TRX and glutathione pathways are essential for postembryonic meristematic activities. Here, we show by associating TRX reductases (ntra ntrb) and glutathione biosynthesis (cad2) mutations that these two thiol reduction pathways interfere with developmental processes through modulation of auxin signaling. The triple ntra ntrb cad2 mutant develops normally at the rosette stage, undergoes the floral transition, but produces almost naked stems, reminiscent of the phenotype of several mutants affected in auxin transport or biosynthesis. In addition, the ntra ntrb cad2 mutant shows a loss of apical dominance, vasculature defects, and reduced secondary root production, several phenotypes tightly regulated by auxin. We further show that auxin transport capacities and auxin levels are perturbed in the mutant, suggesting that the NTR-glutathione pathways alter both auxin transport and metabolism. Analysis of ntr and glutathione biosynthesis mutants suggests that glutathione homeostasis plays a major role in auxin transport as both NTR and glutathione pathways are involved in auxin homeostasis.     

Studies of Acanthodactyla in Tunisia. II. Biometrical relations

The four species of the g. Acanthodactylus Wieg., 1834 occuring in Tunisia are quite individualized by their biometrical relations which, moreover, allow to bring out their relationships. The size of the upper quarter in our sampling oppose two groups of two species each one. The distribution of the ratio between the length of the body and that of the tail place apart A. boskianus from the three other species in a more marked way for adults of both sexes than for juveniles.     

Protein and energy needs for maintenance and growth of Nile tilapia (Oreochromis niloticus)

A trial was undertaken with juvenile Nile tilapia fed graded levels of dietary protein (0–35% DP) over 7 weeks (28°C). Measurements of nitrogen and energy utilization were made using data on ADC, comparative carcass analyses, nitrogen excretion and oxygen uptake. Data indicate that the daily protein intake for maximum N gain was c. 12 g/kg/d and the maintenance protein requirements were about of 2g/kg/d. The optimal DP/DE ratio was found to be 18mg/kJ. Differences were observed in the data on endogenous nitrogen and energy utilization depending on the dietary treatments as well as on the criteria used.     

Obligately and facultatively autotrophic,sulfur- and hydrogen-oxidizing thermophilic bacteria isolated from hot composts

A variety of autotrophic, sulfur- and hydrogen-oxidizing thermophilic bacteria were isolated from thermogenic composts at temperatures of 60–80° C. All were penicillin G sensitive, which proves that they belong to the Bacteria domain. The obligately autotrophic, non-spore-forming strains were gram-negative rods growing at 60–80°C, with an optimum at 70–75°C, but only under microaerophilic conditions (5 kPa oxygen). These strains had similar DNA G+C content (34.7–37.6 mol%) and showed a high DNA:DNA homology (70–87%) with Hydrogenobacter strains isolated from geothermal areas. The facultatively autotrophic strains isolated from hot composts were gram-variable rods that formed spherical and terminal endospores, except for one strain. The strains grew at 55–75° C, with an optimum at 65–70° C. These bacteria were able to grow heterotrophically, or autotrophically with hydrogen; however, they oxidized thiosulfate under mixotrophic growth conditions (e.g. pyruvate or hydrogen plus thiosulfate). These strains had similar DNA G+C content (60–64 mol%) to and high DNA:DNA homology (> 75%) with the reference strain of Bacillus schlegelii. This is the first report of thermogenic composts as habitats of thermophilic sulfur- and hydrogen-oxidizing bacteria, which to date have been known only from geothermal manifestations. This contrasts with the generally held belief that thermogenic composts at temperatures above 60° C support only a very low diversity of obligatory heterotrophic thermophiles related to Bacillus stearothermophilus. Received: 20 July 1995 / Accepted: 25 September 1995     

Medical student fitness to practise committees at UK medical schools

The fabric of science is changing, driven by a revolution in digital technologies that facilitate the acquisition and communication of massive amounts of data. This is changing the nature of collaboration and expanding opportunities to participate in science. If digital technologies are the engine of this revolution, digital data are its fuel. But for many scientific disciplines, this fuel is in short supply. The publication of primary data is not a universal or mandatory part of science, and despite policies and proclamations to the contrary, calls to make data publicly available have largely gone unheeded. In this short essay I consider why, and explore some of the challenges that lie ahead, as we work toward a database of everything.     

Growth and development of root systems: Geometrical and structural aspects

The agronomist who wants to study the nutrient and water uptake of roots needs a quantitative three-dimensional dynamic model of the structure of root systems.The model presented takes into account current knowledge about the morphogenesis of root systems. It describes the root system as a set of root axes, characterised by their orders. The morphogenetic properties of root axes differ according to their order. The axes of order 1 are directly inserted on the stem, the axes of order 2 are inserted on axes of order 1, and so on. They tend to be more plagiotropec and to have less vascular bundles as the order increases.The evolution of the simulated structure is achieved by three processes: emission of new root axes from the shoot, growth and branching of existing root axes. The elongation of an axis depends on its order and on local growing conditions. Branches appear acropetally at a specified distance from the apex and from former branches, along ranks facing xylem poles, with a branching angle specific of their order.From the three-dimensional branched structures simulated by the model, various outputs, such as kinetics of growth and development, root profiles or cross-section maps can be computed, compared to observed data and used as inputs in uptake models. Some examples of such possible outputs are presented.

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Résumé L'agronome qui veut étudier l'absorption hydrique et minérale des racines a besoin d'un modèle dynamique tri-dimensionnel de la structure du système racinaire.Le modèle présentd est fondé sur les connaissances actuelles sur la morphogenèse racinaire. Le système racinaire y est représenté comme un ensemble d'axes caractérisés par leur ordre. En effet, les propriétés morphogénétiques des racines varient d'un ordre d l'autre. Les axes d'ordre 1 sont insérés directement sur la tige, les axes d'ordre 2 sur les axes d'ordre 1, et ainsi de suite. Les axes tendent à être de plus en plus plagiotropes et à avoir de moins en moins de faisceaux vasculaires quand l'ordre augmente.Trois processus interviennent pour faire évoluer la structure racinaire simulée au cours du temps: l'émission de nouveaux axes racinaires à partir des tiges, la croissance, et la ramification des axes

     

Dictyostelium Tom1 Participates to an Ancestral ESCRT-0 Complex

Sorting of ubiquitinated proteins to multivesicular bodies (MVBs) in mammalian cells relies on proteins with a Vps27/Hrs/STAM (VHS) domain. Here, we show that the amoeba Dictyostelium presents only one protein with a VHS domain: DdTom1. We demonstrate that the VHS domain of DdTom1 is followed by a Golgi-localized, γ-ear-containing, ADP-ribosylation-factor-binding and Tom1 (GAT) domain that binds ubiquitin, and by a non-conserved C-terminal domain that can recruit clathrin, EGFr pathway substrate 15 and tumor susceptibility gene 101, a component of the MVB biogenesis machinery [endosomal complexes required for transport (ESCRT) complexes]. Both VHS and GAT domains interact with phospholipids and therefore could ensure the recruitment of DdTom1 to endosomal membranes. We propose that DdTom1 participates in an ancestral ESCRT-0 complex implicated in the sorting of ubiquitinated proteins into MVBs.     

Comments on oral grooming by patas monkeys,including a comparison with rhesus macaques

Observations of the motor patterns used by patas monkeys during allogrooming indicate that this species uses oral movements much more than previously believed. Compared to rhesus macaques, patas show more mouthpicks and licks, and fewer handpicks. Despite behavioral and anatomical evidence for good precision gripping, patas usually remove debris from a partner's fur orally rather than manually.